1. Field of the Invention
The present invention relates to solid detergent compositions comprising at least one biodegradable polycarboxylic polymer in a water-insoluble form, compatible with prolonged storage thereof.
2. Description of the Prior Art
Typical detergent compositions incorporate many reagents, each of which being responsible for a clearly specific function. Among these conventional reagents, particularly significant is the detergent builder.
By "builder" is intended any constituent which improves or enhances the performance of the surface-active agents, or surfactants, of a detergent composition. In general, a builder serves many functions:
(a) it ensures, in a washing medium, the removal of the undesirable ions, especially alkaline earth metal (calcium, magnesium) ions, by sequestration, complexation or precipitation in order to prevent the precipitation of the anionic surfactants. PA1 (b) it provides a reserve of alkalinity and ionic strength, PA1 (c) it maintains the dirt extracted in suspension, and PA1 (d) it prevents inorganic incrustation of the washing. PA1 (a) partially or completely, in the form of one of the water-insoluble inorganic salts thereof, or PA1 (a) anionic surfactants of the types comprising soaps and alkali metals (alkali metal salts of C.sub.8 -C.sub.24 fatty acids), alkali metal sulfonates (C.sub.8 -C.sub.13 alkylbenzenesulfonates, C.sub.12 -C.sub.16 alkylsulfonates, sulfated C.sub.6 -C.sub.16 fatty alcohols, sulfated C.sub.8 -C.sub.13 alkylphenols), alkali metal sulfosuccinates (C.sub.12 -C.sub.16 alkylsulfosuccinates), and the like; PA1 (b) nonionic surfactants of the types comprising polyoxyethylenated C.sub.6 -C.sub.12 alkylphenols, oxyethylenated C.sub.8 -C.sub.22 aliphatic alcohols, ethylene oxide/propylene oxide block copolymers, optionally polyoxyethylenated carboxylic acid amides; PA1 (c) amphoteric surfactants of the alkyldimethylbetaine type; PA1 (d) cationic surfactants of the alkyltrimethylammonium or alkyldimethylammonium chloride or bromide types. PA1 (1) detergent builders of the types comprising: PA1 (2) corrosion inhibitors such as silicates in an amount of up to about 25% of the total weight of the detergent composition; PA1 (3) bleaching agents of the perborate, chloroisocyanate or N,N,N',N'-tetraacetylethylenediamine (TAED) types in an amount of up to about 30% of the total weight of the detergent composition; PA1 (4) antiredeposition agents of the carboxymethylcellulose or methylcellulose types in amounts which may range up to about 5% of the total weight of the detergent composition; PA1 (5) anti-incrustation agents of the acrylic acid and maleic anhydride copolymer types in an amount which may range up to about 10% of the total weight of the detergent composition; PA1 (6) fillers of the sodium sulfate type in an amount which may range up to 50% of the total weight of the detergent composition.
Tripolyphosphates have long been the builders most conventionally incorporated in detergent compositions and washing products. Nevertheless, these are partly responsible for eutrophication of lakes and waters flowing slowly, when they are not sufficiently removed by water treatment plants. Consequently, efforts have been expended to replace the tripolyphosphates, whether partially or totally.
Zeolites alone cannot replace the tripolyphosphates, their efficacy has to be reinforced by other additives.
Copolymers of acrylic acid and maleic anhydride (or their alkali metal or ammonium salts) have been described (European Patent No. 25,551) as inhibitors of incrustation.
However, these acrylic acid and maleic anhydride copolymers, as well as the zeolites, are not subject to biodegradation in the natural environment.
With the objective to satisfy recent ecological requirements, peptide polymers of the amino acid polymer or copolymer type have also been described as builders.
In particular, sodium polyaspartates and polyglutamates, which are of interest because of their total biodegradability, exhibit good builder activity (U.S. Pat. No. 4,428,749). It has been demonstrated that it is the negatively charged form of these compounds which is the active species in the builder function.
Unfortunately, the water-soluble salts of these peptide polymers are unsuited for prolonged storage in solid detergent formulations. Rapidly, they tend to become hydrolyzed and then to become degraded upon contact with oxidizing and basic agents which are also present in the washing formula. After one month of storage, these compounds are incapable of serving a builder function.